Biomedical Engineering Reference
In-Depth Information
6.3.2 EMG Electrode Placement
Two different muscle groups were selected for the detection of hand opening and
hand grasp intention. As shown in the
Figure 6.8
,
the EMG signals were collected
from the extensor digitorum (ED) and the abductor pollicis brevis (APB). The ED
signal was used for the control of hand opening while the APB signal was used for
the control of hand grasp.
Figure 6.9
displays the recorded EMG signals from the
ED and APB muscles during a hand opening and hand grasp tasks.
6.3.3 Maximum Voluntary Contraction
Maximum voluntary contraction (MVC) can be used to evaluate the muscle
strength of each subject every time at the beginning of the training. And the mea-
sured EMG signals of the MVC would be used for the normalization of the EMG
signals for the control strategies. In order to measure the MVC more accurately,
the hand rehabilitation robot would position the subject fingers randomly into
5 different hand positions according to the normalized ROM (ie. 0% means full
palmar grasp or pinch while 100% means full hand opening) and the subject was
asked to do two times MVC for hand grasp as well as two times MVC for hand
opening.
Ref
APB
ED
Figure 6.8
The setup showing the position of electrodes (APB, ED and reference).
ED
2
Hand
opening
1
0
-1
-2
0
0.5
1
1.5
2
2.5
3
Time (ms )
x 10
4
Hand grasp
APB
2
1
0
-1
-2
0
0.5
1
1.5
2
2.5
3
Time (ms )
x 10
4
Figure 6.9
The EMG signals recorded from the ED and APB muscles during hand opening
and hand grasp.
